All chlamydial species are obligate intracellular bacterial parasites of eukaryotic cells, and all are pathogenic to their various hosts. In addition to their known etiologic roles in elicitation of various acute diseases, the human pathogens C. trachomatis (CT) and C. pneumoniae (CP) have been shown to cause, or are strongly associated with, diverse chronic clinical entities. Such conditions are often caused by persistent infection.
Many studies indicate, however, that existing antimicrobial drugs are ineffective against such persistent chlamydial infections, and neither C. trachomatis nor C. pneumoniae requires an animal reservoir for maintenance. Because persistent chlamydial infections are highly prevalent and can have severe chronic disease sequelae, treatments to eradicate such persistent infections are urgently needed.